Cappelen et al. (2015) open their paper, “Fairness is intuitive,” with the observation, “A key question in the social sciences is whether it is intuitive to behave in a fair manner or whether fair behavior requires active self-control” (p. 2). They purport to offer “evidence showing that fair behavior is intuitive to most people” (p. 1). Their premise is that deciding by intuition is faster than deciding by deliberation. While this premise in and on itself is rather uncontroversial—the conclusion that (...) they draw from it is not: “Since a decision that relies on intuition is typically made faster than a decision that relies on deliberation, the response time of a fair decision relative to a selfish decision provides an important indication of the intuitiveness of fair behavior” (p. 2). This reasoning, in fact, amounts to a reverse inference fallacy. ‘Intuitive’ may mean ‘fast’, but this would not imply that ‘fast’ means ‘intuitive’. However, we may ask, under which empirical conditions might we be allowed to draw the inference of ‘intuitive’ from ‘fast’? Naturally, these conditions would require that ‘fast’ rule out ‘deliberative’. To achieve this, we would need information beyond relative response speed alone—such as absolute decision times. And this begs the question, which range of decision times would rule out ‘deliberative’—or at the very least, render it improbable? Although the precise cut-off for deliberative decisions may be difficult to establish (see e.g., Schnei... (shrink)